Thoughts on Transit and Urban Form

Hypothesis: Regular frequent transit service remains feasible even in single family homes in neighborhoods with a modicum of density.

The Land Use

Consider the 1 mile grid landscape that is common in the post-Revolutionary United States due to the Northwest Ordinance and the ease of development. The is roughly the streetcar era land use design.

While there are a variety of ways this grid can be carved up, one common way is to have

  • 10 cross-streets per mile of grid long direction (520′ )
  • 20 cross-streets per mile of grid in short direction (260′ )

This arrangement produces 200 blocks per square mile. The size of each block is:

  • 520′ x 260′ block (center line – center line)
  • 480′ x 240′ block (edge to edge), allowing space for roads.

If houses have a 40’ frontage with 110′ depth ( allowing 20′ for alley?) = 4,400 sq. ft. (~1/10 acre)

Note there are  640 acres per square mile and 43,560 square feet acre per acre.

This spacing gives 12 houses per block face long direction, or 24 houses per block. In this configuration, no houses face the short direction. Obviously this can be adjusted.

If there were only housing, this would give 4,800 houses per square mile

At 2 persons per household (which is definitely on the low side for single family homes, this gives us 9,600 PPSM in single family homes at typical built density. At 5 persons per household, this leads to 24,000 PPSM.

At 5 persons per household, we could increase lot size to 1/4 acre (neglecting roads) and still can get 2,560 houses per square mile  or 12,800 PPSM.

While some space is devoted to schools, parks, retail, commercial, and industrial activity, among other uses, I hope this is persuasive that 10,000 PPSM is feasible over large areas without being Manhattan-like high density. The City of Minneapolis for instance according to the 2010 Census has a density of 7,417 PPSM. At its peak population, it had over 10,000 PPSM.

Elements of Access: Transport Planning for Engineers, Transport Engineering for Planners. By David M. Levinson, Wes Marshall, Kay Axhausen.
Elements of Access: Transport Planning for Engineers, Transport Engineering for Planners. By David M. Levinson, Wes Marshall, Kay Axhausen.

The Transit

The target density for successful transit is often given as 10,000 persons per square mile (PPSM), as per Zupan and Pushkarev (also discussed here).

If we assume that every person originates lots of short trips (which can be dealt with by walking or biking) and one long trip per day (say going to work), the 10,000 PPSM would generate 10,000 transit trips per square mile. So we have 10,000 Boardings. This is roughly streetcar era demand in cities.

If we space transit routes on the 1/2 mile routes (as was typical of streetcars) both east-west and north-south, with stops where transit routes crossed and half-way between (i.e. 1/4 mile spacing between stops), the area is served by 21 stops. The four stops at the outer corners are shared with 4 other areas, and the 8 non-corner stops at the perimeter are shared with 2 other areas, while 5 stops are internal to the 1 mile square, gives us 12 equivalent dedicated stops for the area.

With 10,000 PPSM and 12 stops, each stop serves 833 people per day. If transit vehicles carry 50 people each, that is 17 full transit vehicles per day. Of course transit vehicles do not generally fill up at one transit stop, and over a 17 hour day, this would be 1 transit vehicle every hour. If instead we wanted service at 10 minute headways, but full vehicles, we would expect each vehicle to fill up 1/6 of its load at each stop (or about 8 passengers per stop). That would be a much higher load factor than generally observed.

The maximum walking distance to a transit stop would be (by Pythagoras SQRT of 0.25^2 + 0.25^2 =) 0.35 miles.

The Car

So what guarantees people will make 1 transit trip per day? If there is no good alternative, this is an easy choice. Today, this depends. The argument for using transit is that in our idealized grid-like city with a grid-like transit system, the transit system is as direct as every other mode, so there is no lost distance due to circuity. The only lost time is the schedule delay (which is a maximum on average of 5 minutes, less if people can time their wait to match the transit vehicle), and the time when the vehicle is stopped (and accelerating and decelerating) boarding and alighting passengers, which we know can be faster if people pre-pay, and the transfer time between vehicles (with a maximum of one transfer in the idealized grid, again with a maximum on average of 5 minutes, less if the routes are timed well). Finally with any transit advantages (e.g. signal timing priority, exclusive lane or stopping in lane, as opposed to weaving into stops) transit can recover some of the time lost vis-a-vis the automobile.


Where transit is better (faster, cheaper) than alternatives, and frequent enough, people will use it in large numbers. This is observed daily in large cities. Thus it must be feasible to obtain such faster, cheaper, frequent enough service levels. In most places in the US, the transit service and ridership is not there. Let’s work through an example.

For a five mile trip, there will be about 20 stops at 1/4 mile stop spacing. If each stop results in 30 seconds lost time (2-3 seconds per boarding plus acceleration/deceleration), that is 10 minutes of time lost there.  This will generally be slower than an automobile, even with  stop signs or red lights every 1/4 mile, as the time spent stop at the stop will be less than for transit, even with pre-payment. (Unless the auto is stuck behind a transit vehicle and cannot pass).

Initial schedule delay is 5 minutes assuming random arrivals.

Walk access time of (let’s say 1/2 of 0.35 miles or 0.18 miles at 3 miles per hour) is about 4 minutes. This is obviously farther than from the front door to a parked car at the home end. Destination walk egress time is probably similar  for most people. For transit to downtown, lower for transit (and higher for the parked car).

Transfer time is also non-trivial, and can be as high as another 5 minutes if it is effectively uncoordinated.

So now even with our idealized transit system we have lost something like 10+5+4+5+4 minutes or 28 minutes compared with the car for a 5 mile trip. At a value of time of $15/hour ($0.25/minute) this is the equivalent of $7. If the transit fare is $2, and the cost of gas (at $5/gallon and 25 miles per gallon) is $1 (not even considering carpooling), net additional out-of-pocket cost for transit is now the equivalent of $8. Of course, vehicle ownership ($10-$20/day) can be avoided, as can parking charges. We are not considering externalities, and other costs of vehicles that are not internalized.

The Express

We can make transit faster with express routes on limited access rights-of-way. If demand is high enough, we can make transit go faster, or have an even higher frequency, and stop less often. One disadvantage of express routes is a longer access/egress time (they can’t be spaced as close together if they are to achieve economies of scale, so they are on the mile instead of 1/2 mile spacing at best (as per London)). If that access and/or egress is by transit itself, that imposes additional scheduling time penalties. We can compensate because now our land use changes to take advantage of the express services. At express stations, densities rise. Apartments replace single-family homes. We can also give transit a higher frequency. Express buses and commuter trains often have low frequencies, while modern or modernized subways may have one train every 2 minutes or better. So if we increase the highest distance to a station for 1 mile spacing between stations and 1 mile between routes (so every station is a transfer), the walk access time is 1/2 of the maximum time of SQRT (0.5^2+0.5^2) = 0.71 or 0.35 miles. At 3 mph this is a walk time of  7.1 minutes on each end.

For a 5 mile trip with transfer Our lost time is 2.5 (30 seconds [per stop * 5 stops]) + 1 (schedule delay) + 7 (access) + 1 (transfer delay) + 7 (egress time) = 18.5 minutes. This is less than the local transit service above, and can be reduced for people who live closer to the station rather than spread out uniformly across the landscape. If we have higher travel speeds than auto (let’s say averaging 45 mph while in motion on exclusive right-of-way instead of 30 on surface streets), for a 5 mile trip the express transit time is 6.67 minutes instead of 10 minutes. But this 3.33 minute savings does not outweigh the lost delays due to access and waiting costs. This does not even begin to consider the additional costs of operating express vs. local services, or revenues from the service.

To reduce transportation costs with transit-like services, we can arrange cities linearly, thereby eliminating transfers and reducing access costs. This wastes accessibility for non-transit modes. So optimal urban form depends on the technology you are optimizing for. In a city where driving is perceived to cost $1/trip, and it saves between 18 and 28 minutes per trip, it is no wonder the automobile is the dominant mode for long distance trips even in historically transit advantageous places. Changing that requires changing the perceived (and real) cost of driving for drivers, as there is little that can be done on the transit supply side which will make a significant difference in the absence of that for most markets.

In dense areas, the market takes care of that, with expensive parking. In low density areas, there is enough room for everyone’s car without charging.


I believe systematically re-arranging existing cities for transit (or any mode) is putting the cart before the horse. Transportation should serve activities, and while transportation and land use co-evolve, that co-evolution is slow (over decades) and should be adaptable to alternatives.


A Taxonomy of Modes

A Taxonomy of Modes

A Taxonomy of Modes, Click to See Full Size
A Taxonomy of Modes, Click to See Full Size

I have been playing around with this idea of a Taxonomy of Modes. What characteristics describe and differentiate modes? Every mode must differ from every other mode on at least one dimension (otherwise they would be the same mode). This is analogous to the idea of speciation in biology. The graph above is a first cut at this for surface passenger transportation. I wanted to distinguish primarily on the non-mechanical (non-propulsion) characteristics of the service first. Of course not every possible dimension is identified, and a few of the circles contain multiple modes which are otherwise obviously distinct (e.g. gondolas and subways are much the same from a transportation service perspective but for one is underground and uses a train and the other is suspended by a cable which moves it). I wanted to differentiate things that were qualitatively different rather than quantitatively different.

So the first cut is about time, is a reservation required or not (i.e. does it need some advance planning). The second cut is about time as well, is the service scheduled or dynamic. The third cut is about space, are the routes fixed or dynamic. If the route is fixed, are stops fixed (i.e. does the vehicle stop at every stop, or only when called, like a bus). Otherwise if the routes are dynamic,  things get a bit more ad-hoc, as the key question changes.

Some traditional distinctions (access mode vs. primary mode, such as walk to transit vs. drive to transit) are not distinguished here, rather that would be thought of as at least two trips, one where you walk or drive to some place (with the purpose of changing modes), and second where you take some form of transit.

(A much earlier version of this appears as Theory of Modes (2008))


I welcome comments and ideas for making this more systematic and robust.

Directions for Research in Transport and Land Use

Below I posit some directions for research in transport and land use. Comments welcome.
1. We need more panels and time series and fewer cross-sectional analyses. If we want to establish causation, we need to look across time, otherwise, we are stuck simply with correlations. [And as we know, correlation is not causation]. We need data that examines the evolution and dynamics of transport and land use systems. I have not quite come to the conclusion that all analyses must be temporal (that is rejecting any atemporal analysis), but I am really tempted to do so as a reviewer.
2. We need to improve the scientific rigor of our research. The discipline is ripe for continuing meta-analysis to establish the magnitude of effects, and to reduce the range of estimates (and explain the range that exists through different underlying causal factors).
3. We need to more systematically consider network structure when looking at explanations of travel behavior. This includes measures of topology, morphology, and hierarchy. The measures that have historically been used have been relatively easy to estimate, but don’t get at the gestalt of the network as an integrated system.
4. We need to systematically look at the difference between travelers perceptions of how systems operate and how long are travel times, and what we analysts measure. The differences can be systematically explained, at least in part, and people of course make decisions based on how they think the world works, not on how we think it does. We could then examine why perceptions differ from measurements, how much is simply differences in linguistic interpretation (when a trip begins and ends is somewhat ambiguous, e.g.), and how much is differences in time perception, and how much is “rounding” error, and how much is strategic to either impress with the length of the commute (which brings to mind the Four Yorkshiremen sketch) or to exaggerate in order to get sympathy or a policy response.
5. We need to increase the inter-disciplinarity in the study of transport and land use research, with planners, geographers, engineers, economists, and others working together looking at these problems.
6. We need more international and historical cases in the field to build towards a general truth. Reasoning is both inductive and deductive, but so much of what we are doing is complex, one often cannot simply derive from theory whether a change will lead to more or less travel, it depends on parameters, for instance. the fixed costs of engaging in a trip vs. the variable (and non-linear) costs of travel.

In defense of skyways

At In defense of skyways

In defense of skyways

Harrogate  32

Crossposted at streets.mnand transportationist.orgPhotos of skyways by author from Sydney (2), Portland (2), Minneapolis (3), Tokyo (1), and Harrogate (1) respectively.

Everyone seems to be hating on Minneapolis’s world-beating skyway network. Sam Newberg is the latest in a recent post at

Is it Time to Remove Those Pesky Skyways? :

“The following post shares a similar argument as an article I wrote four years ago for the Downtown Journal (in Minneapolis). I was chastised at the time and suppose I will be again. However, with the recent opening of a new, $3 million skyway link to better connect the Accenture tower to adjacent blocks, as well as the new Downtown 2025 Plan taking on the “Skyway Paradox,” I was persuaded to bring it up again.
So here goes:

Isn’t it about time to start removing our skyways? A few years ago, Jen Gehl, a notable and well-respected Danish urbanist, was in town for an Urban Land Institute presentation. He noted downtown Minneapolis was “no longer up to the beat” of other world-class winter cities, blaming the skyways for striking a “defensive posture” against nature. Save for perhaps one bitter cold winter week per year, I couldn’t agree more. It doesn’t make sense to spend more than $1 million per skyway to perpetuate this anti-world class defensive posture. Gehl’s comments made it into the Skyway Conundrum section of the recently-released Downtown 2025 Plan, so someone is listening! While the plan doesn’t suggest removal, at least they admit the problem, and that, my friends, is the first step to recovery.”

I don’t go downtown much for a variety of reasons, but pedestrian traffic-starved streets are not that reason. Following the model of Victor Gruen, downtown business interests made a decision in the early 1960s to build skyscrapers and skyways and reinforced that decisions continuously. While I am not convinced building skyscrapers was economically wise, given skyscrapers and an arterial street network on which every street and avenue is an entrance or exit to a radial freeway, skyways are a reasonable way to connect buildings. In economic jargon, while no cars downtown might be a “first-best” solution for pedestrians, we don’t live in that world. Given the world where cars dominate streets, a pedestrian-only level is a viable “second-best” solution.

  • Why should all of the modes interact on all levels. In principle, I like shared space as much as anyone, but I don’t like walking on a sidewalk next to 3 or 4 or 5 lanes of motorized traffic, why should I be confined to a narrow building hugging strip rather than travel on a strictly pedestrian level.
  • Tall buildings should generate sufficient traffic to support retail on both the street level and the internal skyway level. In Planning for Place and Plexus we have a box “Ground Floor Retail Everywhere” which estimated that if all retail trips were home-based, 10 story apartment buildings would be sufficient to generate 1 floor of retail. A similar calculation could be done for non-home based (i.e. work-based) retail trips, and given the higher density of people per square foot in office buildings, should generate similar numbers. Short buildings don’t justify skyways, but tall buildings do.
  • Skyways reduce inter-building transportation costs. This should increase inter-building activity and thus economies of agglomeration. Given the only purpose of cities is to connect people at low cost for some mutual advantage, the better cities connect people, the better off everyone is.

I have coauthored two papersabout their evolution, I encourage you all to read the first: Corbett et al. (2009)Evolution of the second-story city: the Minneapolis Skyway System.
Environment and Planning B: Planning and Design volume 36, pages 711 – 724, which goes into the history of the Minneapolis system.


Could the skyways be better. Of course. Some ideas:

  • First, they can better connect to the street network with staircases or lifts adjacent to the sidewalks.
  • Second, they can follow a more regular topology. More importantly the internal skyway level network inside the buildings themselves could be far more navigable than it is. While it is fine for regular commuters who learn the ins and outs, its medieval labyrinth is horrible for the unfamiliar traveler.
  • Third, perhaps the skyway level should be on the 10th or 20th floor instead of the 2nd (The Petronas Towers at Kuala Lampur puts them at the 41st floor). This would require more coordination, but may be more useful in reducing the total amount of vertical movement required for inter-building personal transportation. It is probably a bit late to retrofit Minneapolis, but should be considered in cities newly adopting skyways.

Skyways are Minneapolis’s Cable Cars, our London Underground or Route-Master Bus, our Venetian Canals. Skyways are the iconic transportation system of Minneapolis. With all else (roads, LRT, etc.) we are copy cats. We need to embrace skyways as such, and not listen to others who want Minneapolis to fit into the conventions of relatively weather-less European cities.

Peak Drive-Thru

Cross-posted at and

Drive-thru Wells Fargo at Emerald and University Ave SE, Minneapolis
Drive-thru Wells Fargo at Emerald and University Ave SE, Minneapolis

Wells Fargo Bank has shuttered the drive-thru bank part of its branch at University and Emerald in Minneapolis (on the St. Paul City Line). [Google Street View image shown.]
This may be for several reasons, the branch is immediately across the street from a Central Corridor LRT station (under construction), its road access has consequently been constricted. It would make a nice redevelopment opportunity, so this may simply be a real estate transaction. But perhaps there are other reasons. We have achieved peak travel in the US, and internet and electronic banking has replaced much drive-thru business.
I, like many pedestrians and bicyclists, am annoyed with the hostility the drive-thru gives to non-auto modes. I was reprimanded for walking up to a drive-thru ATM at a Maryland National Bank in Columbia (after many acquisitions, now part of Bank of America) … of course there was no walk-up ATM there, or I would have used that. If I don’t want to or can’t deal with a person, I still have to walk-up to the drive-thru ATM at my Credit Union on University Avenue, which still does not have a walk-up (and their machine looks circa 1980). The annoying part is not just the wrong height of the ATM and the poor User Interface, it is the cross-subsidy non-driving customers give to the driving customers, who pay no extra for the larger building and infrastructure they require.
Drive-thru businesses have a long history in the US, dating at least from 1930 in the banking sector. Obviously gas stations were drive-thru, and I suppose it expanded from there. I had a fascination with these types of businesses as a child, both because of their (at least banks) use of pneumatic tubes, and just because of the futuristic feeling one had doing business from a car. I was impressed when I visited my aunt who went to a drive-thru dairy store in the Philadelphia suburbs. In the planned community of Columbia, Maryland, we did not have these, though drive-thru banks were allowed in the Village Centers, at first drive-thru restaurants were not, and certainly not drive-thru groceries. We eventually got a Fotomat knock-off, and I was fascinated by the miniaturization of retail.
Visiting some southern town (I’m guessing Tallahassee, but it was a couple of decades ago) when I was in college, there was the drive-thru liquor and gun store (like this one, but different), everything for good-ole-boys to have a really good time on a Friday night. There is also a drive-thru romance store in Alabama, which seems less awful and gives a different meaning to the term ‘quickie’.
Of course there are drive-thru ‘quick-serve’ restaurants, and even Starbucks, which was once aiming to be a third space, in addition to these other oddball collections. Tom Vanderbilt in a Slate article on the subject notes McDonald’s gets 65 percent of US sales from drive-thru.
An hour of Googling does not give me a solid number of drive-thrus in the US, but Rheitt Allain estimates about 100,000.

The End of Traffic and the Future of Access: A Roadmap to the New Transport Landscape. By David M. Levinson and Kevin J. Krizek.
The End of Traffic and the Future of Access: A Roadmap to the New Transport Landscape. By David M. Levinson and Kevin J. Krizek.

There is better data on all restaurants, apparently the number of restaurants in the US is dropping about 2 percent according to Nation’s Restaurant News to 574,050 in 2011. One assumes drive-thrus are dropping as well, though independents are experiencing most of the fall. Overall, spending for food away from home has been dropping the past few years as a function of the recession and high gas prices.
The total number of bank branches seems to have peaked in 2009 (i.e. it was down in 2010, whether this is short term or permanent is of course unclear), while the number of institutions is way off the peak due to consolidation and merger.
All of this portends that the US may have saturated the drive-thru market, and the direction is moving down. It is still speculative, and future data will be required to confirm this, but if so, we may be facing a more walk-up America.

A Dictionary Of Transport Analysis

I have a couple of chapters (mine are under a Creative Commons license!) in the Recently published: Button, Kenneth, Henry Vega, Peter Nijkamp (2011) A Dictionary Of Transport Analysis Edward Elgar Publishing:

“This concise and clearly focused Dictionary, with contributions by the leading authorities in their fields, brings order and clarity to a topic that can suffer from confusion over terminology and concepts.
It provides a bridge between the academic disciplines involved and illustrates the application of transportation policy that crosses a variety of administrative divisions. Cutting through jargon, the entries concentrate on the social science aspects of transportation analysis, defining many of the terms used in transportation, and providing valuable information on some of the major institutions and technologies affecting this sector
This concise and comprehensive Dictionary will be an invaluable addition to libraries and research institutes and a helpful resource for anyone with an interest in the analysis of transport.”

World Society for Transport and Land Use Research (WSTLUR)

The inaugural World Symposium on Transport and Land Use Research
(WSTLUR) was held in Whistler, BC on July 27-30, featuring over 40
peer reviewed papers (submitted to the Journal of Land Use and
Transport, and keynote addresses from Ed Glaeser (Harvard),
Robert Cervero (UC Berkeley) and David Bannister (Oxford). Please see for the program and links to presentations and even
audio recordings of the keynotes.
The steering committee is now forming the World Society for Transport
and Land Use Research (WSTLUR), who will be charged with organizing a
subsequent symposium in 2014 and other aims of the Society. The
mission statement—broadly, to cultivate an interdisciplinary research
community/agenda— is below.
Members of the society will elect the board (11 seats are open); the
board will then select its officers. (Please see bylaws posted at ; Kevin J. Krizek, University of Colorado, has been
appointed chair of the elections committee). If you are interested in
participating in this exciting international endeavor, we encourage
you to become a member of the society. Attendees of the World Symposium on Transport and Land Use Research
(WSTLUR) are already members.
Fees are $75 for three years
and can be registered by going to .
Elections for the board will commence Sept 15, 2011; if you are
interested in becoming a member and voting in the election, please
become a member by September 9, 2011.
If you or someone you know is interested in serving on the board,
please send a nomination to Kevin J. Krizek ( by
September 9. Anyone can nominate members for the board, however,
nominees must be (or become) a registered member of the society. A nomination
consists of:
-Name of the nominee
-Current position and affiliation
-A narrative (not to exceed 80 words and written in the third person),
describing the nominee’s activities, broadly speaking, in the area of
integrated transport-land use research.
Self nominations are allowed and all nominations need to be accepted
by the nominee. Please end only one email to Kevin J. Krizek
documenting the above process with the nominee’s full name in the
subject heading. (Self nominees would need to send only one email;
others would send one email with acceptance embedded).
Should you have any questions, please contact
Kevin J. Krizek (University of Colorado) at
The purpose of WSTLUR is to promote the understanding and analysis of
the interdisciplinary interactions of transport and land use and to
provide a forum for debate and a mechanism for the dissemination of
information. More specifically the aims include:
1. The exchange and dissemination of information at an international
level on all aspects of the theory, analysis, modeling, and evaluation
of transport-land use interactions and related policy.
2. The encouragement of high-quality research and application in the
above areas, through debates, publication, and promotion.
3. The provision of a clearinghouse for information on recent
developments in the field and to foster contacts among professionals
within and between various countries and different disciplines.
4. The promotion of international conferences, seminars, and workshops
on all aspects of transport-land use interaction.
5. The representation of the viewpoints of members to appropriate
national and international bodies, as required by the membership.
6. The preparation of regular communications to facilitate the above aims.

City dwellers produce as much CO2 as countryside people do: study

Via Good, Physorg reports on a recent paper: City dwellers produce as much CO2 as countryside people do: study:

“Most previous studies have indicated that people in cities have a smaller carbon footprint than people who live in the country. By using more complex methods of analysis than in the past, scientists at Aalto University in Finland have discovered that people’s carbon emissions are practically the same in the city and in the rural areas. More than anything else, CO2 emissions that cause climate change are dependent upon how much goods and services people consume, not where they live.”

Full article Jukka Heinonen and Seppo Junnila (2011) Implications of urban structure on carbon consumption in metropolitan areas Environ. Res. Lett. 6 (January-March 2011) 014018

If you buy Life-Cycle Analysis, this is one strike against sanctimonious urbanites in the GHG blame game.

Transportation at TED

Some TED Talks about Transportation
Bill Ford:
Shai Agassi
Robin Chase
Sebastian Thrun
Dennis Hong
Dean Kaman
Paul Moller
Gary Lauder
Jaime Lerner
Steven Levitt